Would you let the brick layer detail your air barrier or your drywaller? Let’s be frank, air barrier detailing in Ontario kinda goes like the Abbot and Costello “Who’s on First Base?” skit. On the job site, no one really knows where the air barrier is unless the detailing is being managed and specifically detailed by the site supervisor.
There’s so much confusion about what the air barrier is and it’s clear even building inspectors are equally confused given the short shrift they give to the building envelope. Take this house being built right now in the Junction.
First, let us all agree that it’s significantly easier to get a continuous air seal on the outside of the building as opposed to the inside. Second, let us all agree that if the air barrier is on the outside of the building, electricians, plumbers, alarm, communications and HVAC subs won’t make Swiss cheese out of it.
Because Tyvek Home Wrap is not listed as an air barrier, it serves only to shed any water that gets through the brick, but in this case not on even that because the openings weren’t sealed with tape per the manufacturer’s specifications. The irony is that this new build used plywood as its sheathing – the builder could have simply taped up the seams of the plywood to form an air barrier – but didn’t. The builder could have also used a product like TYPAR, taped the seams and voila – air barrier installed on the outside!
The only option for this builder now is to use a 6mil poly on the inside as the air barrier, which means that the 6mil needs to be air sealed and clamped where not supported by drywall. Because there is no continuous air barrier yet on this house, even if 2lbs spray foam is installed in the stud bay, they may be compelled to install a 6mil poly over the spray foam as an air barrier which needs to be continuously sealed – ie. along the rim joist – which is fiddly to say the least and never gets sealed well. I guess it’s up the the drywaller to detail the vapour barrier on this job- good luck!